Turbocharged four stroke cycle fuel injection engine



April 18, 1961 F. HoMoLA 'E1-AL 2,979,887

TURBOCHARGED FOUR STROKE CYCLE FUEL INJECTION ENGINE 2 Sheets-Share?l 1 Filed Nov. 4, 1957 April 18, 1961 F. HoMoLA ET AL 2,979,887

TURBOCHARGED FOUR STROKE CYCLE FUEL INJECTION ENGINE HIIIIIIIII HII Illlll Unit TURBOCHARGED FOUR STROKE CYCLE FUEL INJECTION ENGINE Friedrich Homola, Koln-Dellbruck, Georg Oberlnder,

Koln-Riehl, and Otto Elwert, Koln-Lindenthal, Germany, assignors to Klockner-Humboldt-Deutz, Aktiengesellschaft, Koln, Germany The present invention relates to a four-stroke cycle internal combustion engine with fuel injection, which is equipped with a plurality of mechanically independent exhaust gas turbines arranged in such a manner that the exhaust gas flows from one exhaust gas turbine into the other. The arrangement is such that the turbine or turbines into which the exhaust gas ows vfirst, has its or have their useful energy output conveyed for instance to the crankshaft of the internal combustion engine, Whereas that turbine which obtains the exhaust gas last, drives a charging compressor.

The problem underlying the present invention consists in so designing a supercharged four-stroke cycle internal combustion engine with fuel injection and to drive such engine in such a manner that on one hand high peak pressures will be avoided which in addition to being dependent onv other factors are also dependent on the charging pressure and lead to abnormally greater dimensions of the crank 'gear system with regard to the diameter of the cylinder, while on the other hand favorable fuel consumption will be obtained, as it-was possible heretofore, by an abnormally high supercharge only with correspondingly high peak pressures. u y Y n As a solution to the above mentioned problem, it has heretofore been suggested to arrange a plurality of exhaust gas turbines behind an internal combustion engine in such a way that the exhaust gas flows from one turbine to the other turbine, while the various turbines are mechanically independent of each other.V The exhaust gas turbines through which the exhaust gas passesiirst, convey their output to the -crankshaft of the engine, whereas that turbine through which the exhaustl gas passes States P@fhf O 2,979,887 Paf-fente@ Apr. 18,1961..

increases, and thus a lower specific fuel consumption will result. These considerations are valid essentially for internal combustion engines in which the exhaust gases are accumulated in front of exhaust gas turbines, and also for engines with impact operation, i.e., such engines in which the kinetic energy of the exhaust gases is partially exploited for driving the turbines. v

It is an object of the present invention to provide a four-stroke cycle internall combustion engine with fuel injection of the above-mentioned type, which will bring about a considerable improvement in the degree of efficiency of such engines. Y

Itis a further objet of this invention to provide a.y four-stroke cycle internal combustion engine as set forth in the preceding paragraph, in which the exhaust valve will over` heretofore known engines of the general type involved be subjected to considerable less thermic stress.

These and other objects and advantages Vof the inven# tion will appear more clearly from the following spec1- tication in connection with the accompanying drawings I in which: Y

last drives a supercharging compressor. With a4 particular engine of this type, the exhaust gas turbine conveying its output to the crankshaft of the `internal vcombustion enginemay be disconnected so that'no exhaust gas will pass therethrough and no mechanical connection will exist Fig. l illustrates a graph indicating the operation of' an nternalcombustion engine according tothe invention. t l Y Y Y Y Fig; 2 is a top view of an internal combustion engme according to the invention. Y

General arrangement A considerable improvement in the degree of efficiency of a four-stroke cycle internal combustion engine with fuel injection, in which the turbine or turbines Ythrough whichtthe exhaust gases pass first, convey a useful energy output to an element or device of the installation is obtained according to the present invention by the following features:

A. The turbine or turbines through which the exhaust ygases pass tirst haveow passages passed through by the exhaust gases so small in cross sections that the pressure in front of the said turbine or turbines at full load, at which time the charging compressor furnishes the highest charging pressure, will be at least as high as the charging pressure, so that gases are in a manner known per se Vexhausted over the entire exhaust stroke against a pres'- sure, which is at least as high as the charging pressure.

The turbine, which is last to he passed through yby 'exhaust gases and the compressor Adriven Vbysaid turbine, are l*so* designed, that the charging pressure at least vat full load is higherY than the pressure in front of the exhaust gas turbine, which drives theV charging compressor.

C. The pressure, which at the start of the suction stroke of Vthe working piston prevails in the combustion Vchamber of thecylinder, is reduced by the movement of between the said exhaust gas turbine and other elements A of the engine. This disconnection is effected automatically in conformity with the load actingon thevinternal combustion engine. 1 i

These known internal combustion engines, however,

scavenging of the residual gases from the working cylinders can be effected.n On the otherhand, however, an effective scavenging of the dead spaces ofthe cylinder Y is indispensable ifthe weight of load of air and Ythereby also oxygen in the cylinder is to amount to a maximum. The higher this weight, `the greater will be lthe quantity of fuel which can be burned vin each working cycle. 1A greater quantity of burnedfuel produces a highery indicated m ean pressure. Since the frictionylosses remain substantially constant, the mechanical degree of etlipiency v,

the working piston andby an auxiliary outlet valve, opening shortlyvafter the working piston has started its suction stroke, tothe atmospheric pressure or to approximately the pressure prevailing in front of the Ycompressor driving turbine, vbefore the inletrvalve is opened, said' auxiliary outletyalve connectngrthe vcombustion chamber of thecylinderV with the "chamber in frontof said'last mentioned turbine and closes shortly after the inlet valve of the cylinder-is opened. Y

D gThre inlet valve Yis opened only after'thepressure Vin the cylinder has dropped toor below the superchargmgfPICSSUfe--- .Y Y ,t Q The main advantage of the internal combustion engine according to the inyenti'on consists in that a'scaveng'ing `of the residualk gases will be obtained in spite of the fact that the exhaustgas'es will be exhausted by thepiston 'of the engine over thekentire piston stroke against a pressure whichequals or is higher than the superchargin'g pressure, VWith a heretofore known internal combustion enginein which theexhaustgases are exhausted over the entire piston stroke against a pressure which is higher than the supercharging pressure, no scavenging of the residual gases is effected or intended. In view of the fact that with the internal combustion engine according to the invention'the counter-pressure can be increased up to the expansion end pressure of the gases in the cylinder at the end of the working stroke, which stephas heretofore never been materialized, the energy still remaining in said expansion gases can with the engine according to the invention be exploited in 2in-accumulating or damming up operation to a heretofor never obtained degree of efficiency.

A further advantage of the internal combustion engine according to the invention is seen in the low thermic stress of the outlet valve in comparison to the'stress of the outlet valve in such engines in which at the end of the expansion stroke the pressure in the cylinder drops suddenly to such an extent that the exhaust gases are exhausted at high speed and a correspondinglyV large quantity of heat is conveyed to the outlet valve which is heated thereby to a considerable'extent.

Structural arrangement The operation of the internal combustion engine according to the invention will best be understood in `connection with the graph of Fig. l. In connection with this graph, it is assumed for instance that an engine is in- Volved in which the pressure prevailing in the dead spaces of the cylinder at the start of the suction stroke is higher than the charging pressure and by the movement of the working piston and by means of an auxiliary outlet valve is reduced to the pressure prevailing in front of the gas turbine driving the supercharging compressor while the gases are then conveyed into the chamber in front of said turbine.

The graph of Fig. 1 representing an idealized diagram clearly shows the course of the pressure in the cylinder during the change of the charge.

` aereas? With the heretofore customary exhaust turbo supercharging of four-stroke cycle internal combustion engines, the pressure in the cylinder was during the opening of the outlet valve at point 2 reduced substantially to the pressure at point B in front of the turbine, and the exhaust gases were exhausted from the cylinder against the said pressure. The energy of the exhaust gases corresponding to the area Z-B-S-Z could only partially be regained, namely, as far as it occurred in the form of kinetic energy. However, itv is well known that this elfect in the exhaust gas turbine dueto the impact losses brought about by the variable speed or flow of the gases ,through the turbine brings about a reductionin the degree of eiciency of the turbine. Therefore, actually a small fraction only of the said area 2-B-.8--2 can actually be effectively used.V Only a relativelv small nnrtion of the energy, namely that corresponding tothe diagram surface 8-9-0-1is conveyed.totheworking piston by means of the exhaust gas turbine andthe supercharging compressor. Incontrast thereto, with the engine according to thepresent invention,V the exhaust gases are exhausted by the piston against a pressure 2 3 which is higher than the supercharging pressure. In the graph` this counter-pressure equals for instance the eX- pansion end pressure in the cylinder. Whenthe outlet valve is opened, the otherwise shock-likepres'sure associated with supersonic llow and accordingly accompanied by the formation of noise and increasedheating of the outlet valve is completely eliminated. The exhaust work isto be performedV by the piston so that the power output of the crank shaftwill be less. Up to. the time when the outlet valve is closed (atpoint 3), the pressure prevailing in the compression chamber has remained practically unchanged., The gases in the combustion chamber will expand atthe startof the suction strokeof ,p the working piston whilethe valves are still closed and,Vv

'due to the movement of the piston, will perfor'm work.

At "point 4, the auxiliary outlet valve opens and estab- 4 lishes communication between the cylinder chamber and the chamber in front of the turbine driving the compressor so that the pressure in the cylinder drops to the pressure prevailing therein which pressure is lower than the supercharging pressure. Now, the inlet valve opens (point 5), and the scavenging air effects a scavenging operation as long as the auxiliary outlet valve is still open so that the exhaust residual gases are swept out of -the cylinder. At point 6, the auxiliary outlet valve closes again and the charging air will during the remainder of the suction stroke of the piston ow into the cylinder (stroke 7-1). At point 1, the inlet valve closes and the compression stroke starts.

The Work which is to be performed by the piston during the exhaust of the exhaust gases from the cylinder is, as can be seen from the graph of Fig. 1 considerably less than the work which is performed by a turbine in which the expansion of this quantity of exhaust gas 'from the expansion end pressure in the cylinder to the pressure in front of the turbo charger is effected at a satisfactory degree of efficiency. In this way, the expansion energy of the exhaust gases (2-B-8--2) can be exploited in a considerably more economical manner than was the case with the heretofore known type of turbo charging.v

The further expansion of the exhaust gases is effected in the turbine of an exhaust gas turbocharger which may be designed for a supercharging up to In further developing the invention, it is suggested that the auxiliary outlet valve, the opening period of which is kept relatively short so that primary residual gases only will escape, is designed in a manner known p er se as cone valve with a cylindrical control Vextenslon.

The invention may equally successfully be employed Vwith such engines in which the turbine through which the exhaust Ygases pass first conveys its useful power output to vthe .shaft of the internal combustion engine, as well as with such engines in which it directly conveys its useful output to the` next turbine.

In order to improve the scavenging operation, in conformity withA a `further development of the invention, the conduit leading from'the auxiliary outlet valve into the chamber in front of the exhaust gas turbine driving the compressor may in a manner known per se be so dimensioned that the pressure wave entering the conduit when the auxiliary outlet valve Vis opened will, after reflection at the` end ofthe conduit, arrive in the cylinder as alowV pressure wave prior to the Yclosing of the auxiliaryl outlet-valve.

Referring now vto Fig. 2 showing the top view of a six-cylinder four-stroke cycle internal combustion engine, the engine shown therein has veach of itscylinder heads V2, V3, 4,5, 6, and 7 provided with three valves, namely,

-ing the exhaust gases exhausted by the auxiliary valves, "there'is provided a collecting manifold 13 for the lcylinders 2, 3 and 4, whileda ycollecting'manifold i4 Ais provided 'forthe cylinders S, 6 and 7. On the exliaust'side there are furthermore arranged two exhaustgas turbines 15 and 16 which are mechanically independent of each other. The exhaust'gas turbine Vl5 Aconveys its energy output to the crankshaftfof` `the, internal combustion, en-

gine through'` a` transmission comprising the gears 17, 18,19 and 20. .'Ihepower output of the exhaust gas turbine 1`6..drives Va-.compressorl whichconveys charg- Aingair lto the engine `throughkthe conduit ll. Y

Thev turbines 15and 16 are arranged one behind the other in such a way that the exhaust gases received from the collecting manifold 12 first pass through the turbine 15 and then through turbine 16. -From the turbine 16, the exhaust gases pass through a conduit 21. The two exhaust gas collecting manifolds 13 and 14 lead into a chamber 22 in front of the turbine 16 and are so designed that the pressure wave entering the conduitwhen the auxiliary outlet valve of each cylinder is opened will after reflection at the end of the conduit arrive as low pressure wave in the cylinder prior to the closure of the auxiliary outlet valve. The operation of the engine determining the valve control will be ascertained from the graph of Fig. 1 and the description thereof Set forth above. I

It is, of course, to be understood that the present invention is, by no means, limited to the particular construction shown in the drawings but also comprises any modications within the scope of the appended claim.

What we claim is:

In combination in a four stroke cycle internal combustion engine with fuel injection having a cylinder and a piston reciprocably mounted therein: a superchargingl Y compressor, an inlet valve connected to said engine cylinder and with the compressor for receiving air under charging pressure fromthe compressor, a main youtlet valve connected to said cylinder for releasing exhaust gas from the cylinder, ya plurality of exhaust gas turbines mechanically independent of each other but arranged for the serial flow of gas therethrough and connected with said outlet valve so that the exhaust gas from the engine will iiow through the turbines in series, the turbine through which the exhaust gas rst passes being drivingly connected to said engine yto convey energy thereto and having the ilow passages therethrough for gas sufficiently small in cross section so that the pressure at the inlet side of the said turbine at full load, at which the charging pressure is highest, Will be at least as high as the charging pressure, the turbine which the said exhaust gas passes through lastbeing drivingly connected to said compressor for driving the compressor, said compressor and the said driving turbine therefore being so selected that the charging pressure 'developed by the compressor at least at fwll load is higher than the pressure at the inlet of the compressor driving turbine, an auxiliary outlet valve connected to the engine cylinder, said auxiliary outlet valve opening shortly after the working piston has commenced its suction stroke so that the pressure which prevails in the cylinder yat; the start of said suction stroke will be reduced by the movement of the working piston and by the opening of said auxiliary outlet valve, the said pressure prevailing in the cylinder being thus reduced substantially to atmospheric pressure or substantially to the pressure prevailing at the inlet vof said compressor driving turbine, said pressure reduction occurring before said inlet valve commences to open, said outlet valve connecting said cylinder with the inlet side of the compressor driving turbine, and said auxiliary outlet valve closing shortly `after the inlet valve of the cylinder has opened.

References Cited in the le of this patent UNITED STATES PATENTS 1,624,850 Steele Apr. 12, 1927 1,634,797 Newton July 5, 1927 1,849,170 Buchi Mar. 15, 1932 1,895,538 Buchi Jan. 31, 1933 1,994,167 Berstler Mar. 12, 1935 2,131,959 Kadenacy Oct. 4, 1938 FOREIGN PATENTS 457,712 France Sept. 24, 1913 699,846 Great Britain Nov. 18, 1953 

